The present invention relates to a method for removing contaminants from contaminated materials, especially contaminated soils and construction debris, in which the contaminated material after removing coarse particles by screening and breaking, is subjected to a distillation process at a temperature of 300.degree. to 600.degree. C., preferably a vacuum distillation process at a temperature of 350.degree. to 450.degree. C.
It has been known from U.S. Pat. No. 5,056,541 to pretreat contaminated soils containing coarse particles by screening and breaking and subjecting the so treated soils to an extraction process with washing water containing additives, subsequently separating the soils from the washing water, then rinsing with rinsing water and removing the extracted contaminants from the rinsing water by a further cleaning process. In this method the extraction process with washing water optionally containing additives is essentially carried out as a separate process independent from the one or more-step rinsing and sorting process, whereby a finest fraction of a particle size of 150 .mu.m is separated from the soils before the extraction step by dry or wet classifying methods. The dried finest fraction is subsequently subjected to a distillation step. With this known method the cleaning of contaminated soils is possible; however, the known method is disadvantageous with respect to energy consumption and cost factors because the soils which have been separated from coarse particles by screening or breaking are subjected to a substantial pretreatment in the form of extraction, rinsing, and drying processes before the dried finest fraction finally undergoes the distillation step. The disadvantageously high energy costs primarily result from the fact that soils naturally contain approximately 10 to 15% water while the soils being treated according to this known method will have a water contents of at least 30% after the wet washing process, even after undergoing an optimal pressing step in a chamber filter press.
It is therefore an object of the present invention to simplify the method of the prior art and to carry out the pretreatment of the soils containing coarse particles such that the material being subjected to the distillation process will not accumulate water during the pretreatment step.